This specification includes a microfiche appendix containing one (1) sheet of microfiche with thirty-six (36) frames of content.
This invention relates generally to methods and systems of communicating for use with subterranean wells, such as oil or gas wells. The invention relates more particularly, but not by way of limitation, to communicating data to the surface of a well from the vicinity of a three-phase downhole induction motor and connected submersible pump.
Techniques for communicating information in a subterranean well have been applied or disclosed with regard to the various operations of drilling, completing and producing oil or gas wells, for example. Communications can occur between locations within a well or between the surface and downhole. For example, command signals to operate a downhole tool might be sent from the surface or data signals from downhole sensors might be sent to the surface.
One environment of particular relevance to the present invention includes a subterranean well in which a three-phase induction motor drives a submersible pump to pump fluid (e.g., oil) out of the well. Three-phase electricity from a power source at the surface energizes the motor through three conductors of a power cable that extends from the surface to the downhole motor. Downhole conditions to monitor for ensuring proper operation of the motor and pump include pump intake pressure and motor winding temperature.
The foregoing is well-known in the industry, and analog and digital communication techniques have been proposed or developed to transmit data about the aforementioned and other downhole conditions. Despite these prior techniques, there is still the need for a new and improved communication method and system that can provide enhanced speed or resolution for transmitted information.
The present invention meets the aforementioned need by providing a novel and improved method and system of communicating for subterranean wells. The present invention uses both the amplitude and the duration of a pulse to convey information. This enables the information to be transferred more quickly because two items of distinct information can be communication via a single pulse. Alternatively, information can be communicated at the same rate as other single pulse data but with improved resolution.
A method of communicating, for a subterranean well, defined in accordance with the present invention comprises: selecting information to be communicated; and changing at a first location relative to the well an amplitude of a parameter for a specified time duration, wherein the changed amplitude and the specified time duration are derived in response to the selected information and wherein the changed amplitude and-the specified time duration are detectable at a second location relative to the well. In one implementation two distinct items of information can be encoded wherein the information encoded in the amplitude is distinct from the information encoded in the duration. One, more highly resolved, item of information can be defined in that the amplitude and the duration can together represent one aspect of the information to be communicated. Multiple signals can be used to convey the complete information; that is, the amplitude and the duration for a single signal can represent at least part of the information.
The present invention can also be defined as a method of communicating data from a subterranean well having three-phase power conductors connected to a three-phase motor in the well. The magnitude of at least one condition related to the operation of the three-phase motor and a submersible pump connected to the motor is sensed in the well. Encoding occurs in the well such that an amplitude and a duration for at least one electric signal are defined in response to the magnitude of a respective sensed condition. The method further comprises communicating through the three-phase power conductors in response to the encoding. In a particular implementation, communicating through the three-phase power conductors includes changing a voltage on a conductor connected to a neutral point of three windings of the three-phase motor.
The present invention also provides a system for communicating in a subterranean well. The system comprises an information source to provide a signal representing a numerical value to be communicated in a subterranean well. It also comprises an encoder, connected to the information source, to encode the numerical value into at least one amplitude and at least one duration for at least one analog pulse wherein the amplitude and duration for one said analog pulse together define at least part of the numerical value. The system can further comprise: three-phase power conductors disposed in the well; first, second and third windings collectively connected at a common node and individually connected to a respective one of the three-phase power conductors; a first inductor, connected to the common node; a constant d.c. current source connected to the first inductor and an electrical ground; a three-phase motor connected to the three-phase power conductors in the well; a second inductor, connected to a neutral point of windings of the three-phase motor; a transistor connected to the second inductor; and an operational amplifier connected to the transistor, the operational amplifier having an input connected to the encoder.
Therefore, from the foregoing, it is a general object of the present invention to provide a novel and improved method and system of communicating for subterranean wells. Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art when the following description of the preferred embodiments is read in conjunction with the accompanying drawings.